The invention relates to gastroretentive formulations, in particular tablets, and to the process for manufacturing said formulations.
An important factor affecting the absorption of orally administered drug through gastro-intestinal tract is transit time in gastrointestinal tract.
Some active substances, for example metformin and ciprofloxacin, are known as being absorbed only from the stomach to the jejunum, i.e in the upper part of the gastrointestinal tract.
Hence, to achieve maximum efficiency with a minimum of active substance, it would be beneficial that the formulation be retained during a prolonged time in the stomach and allows therein a sustained release of the active substance.
Some attempts have already been done to achieve formulations with such a sustained release in the stomach, either thanks to the use of multilayer tablets such as in U.S. Pat. No. 6,797,283 (Edgren et al.), US patent application 20030232081, or thanks to tablets which are sufficiently small to be ingested and which swell after ingestion such as in U.S. Pat. No. 6,635,280 (Shell et al.) and U.S. Pat. No. 6,660,300 (Timmins et al.), and which further include disintegrating agent and effervescent agent, such as in U.S. Pat. No. 6,261,601 (Talwar et al.).
However, these formulations are not completely satisfactory and it still exists a need for formulations which are able to be retained in the higher part of the gastrointestinal tract and to release the active substance during several hours in the stomach.